1. Field of the Invention
The present invention relates to video display units that can stow and display a monitor.
2. Description of Related Art
To provide added comfort to passengers in an aircraft, the plane is typically provided with television monitors that display movies, etc. The monitors are usually stowed in a cavity in the ceiling of the passenger compartment. The monitors are typically attached to a hinge that allows the monitors to be rotated down into a viewing position. An actuator and a corresponding electric motor are attached to each monitor to rotate the same in and out of the compartment cavity. On occasion the passenger compartment will lose electrical power, in which case it is desirable to retract the monitors into the stowed position. The Federal Aviation Administration (FAA) requires that all monitors be concealed when the compartment loses power, to insure passenger safety.
Present display units have a single band, clock windup type tension spring connected to a ball screw actuator that rotates the monitor into and out of the cavity. The tension spring stores energy when the monitor is rotated into the viewing position and retracts the monitor when the actuator loses power. To lift heavier monitors such as a 16 inch screen, a heavier spring is required to provide the additional torque needed to lift the monitor. The torque of a spring is typically increased by increasing the diameter of the wire. Although the spring constant is increased, the life of the spring decreases because of the higher stress on the wire. Generally speaking the spring constant of a spring is increased by using a thicker wire, the larger wire diameter also increases the stress of the spring producing a dilemma typically encountered in spring design. What is needed is a device with a long life expectancy, that can retract large monitors into a stowing cavity when the actuator becomes inoperative.